/*******************************************************************************
 * Copyright (C) 2007 The University of Manchester
 *
 *  Modifications to the initial code base are copyright of their
 *  respective authors, or their employers as appropriate.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public License
 *  as published by the Free Software Foundation; either version 2.1 of
 *  the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 ******************************************************************************/
package uk.org.taverna.configuration;

import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVPrinter;
import org.apache.log4j.Logger;

/**
 * A utility abstract class that simplifies implementing a Configurable.
 * <br>
 * <p>A concrete version of this class needs to define the name,category,
 * UUID string and the set of default values.</p>
 *
 * @author Stuart Owen
 *
 */
public abstract class AbstractConfigurable implements Configurable {

	private Map<String,String> propertyMap = new HashMap<String, String>();

	private static Logger logger = Logger.getLogger(AbstractConfigurable.class);

	public static final String DELETED_VALUE_CODE = "~~DELETED~~";

	private ConfigurationManager configurationManager;

	public Set<String> getKeys() {
		return getInternalPropertyMap().keySet();
	}

	/**
	 * Constructs the AbstractConfigurable by either reading from a previously stored set of properties,
	 * or by using the default values which results in them being stored for subsequent usage.
	 */
	public AbstractConfigurable(ConfigurationManager configurationManager) {
		this.configurationManager = configurationManager;
		try {
			configurationManager.populate(this);
		} catch (Exception e) {
			logger.error("There was an error reading the properties for the Configurable:"+getFilePrefix(),e);
		}
	}

	public synchronized String getProperty(String key) {
		String val = getInternalPropertyMap().get(key);
		if (val==null) val=getDefaultProperty(key);
		if (DELETED_VALUE_CODE.equals(val)) val=null;
		return val;
	}

	public String getDefaultProperty(String key) {
		return getDefaultPropertyMap().get(key);
	}

	protected void store() {
		try {
			configurationManager.store(this);
		} catch (Exception e) {
			logger.error("There was an error storing the new configuration for: "+this.getFilePrefix(),e);
		}
	}

	public void clear() {
		getInternalPropertyMap().clear();
	}

	public synchronized void setProperty(String key, String value) {
		Object oldValue = getInternalPropertyMap().get(key);
		if (value==null) {
			deleteProperty(key);
		}
		else {
			getInternalPropertyMap().put(key,value);
		}
		if (value==null || !value.equals(oldValue)) {
			store();
		}
	}

	/**
	 * Provides access to the internal map.
	 * <br>
	 * Note that this map will contain entries for deleted values that also have corresponding default values.
	 * For this reason using this map directly is discouraged, and  #getProperty(String)} should be used instead.
	 * @return
	 */
	public Map<String, String> getInternalPropertyMap() {
		return propertyMap;
	}


	public void restoreDefaults() {
		propertyMap.clear();
		propertyMap.putAll(getDefaultPropertyMap());
		store();
	}

	public void deleteProperty(String key) {
		if (getDefaultPropertyMap().containsKey(key)) {
			propertyMap.put(key, DELETED_VALUE_CODE);
		}
		else {
			propertyMap.remove(key);
		}
	}

	/**
	 * Returns an unmodifiable List<String> for the given key. Internally the value is stored as a single String, but converted to a list when calling this method.
	 * <br>
	 * The list is unmodifiable to prevent the mistake of trying <pre>getPropertyStringList(..).add("new element");</pre> which will not affect the stored
	 * list. For the property to be updated this{@link #setPropertyStringList(String, List)} must be used.
	 */
	public List<String> getPropertyStringList(String key) {
		String value = getProperty(key);
		if (value!=null) {
			return Collections.unmodifiableList(fromListText(value));
		}
		else {
			return null;
		}
	}

	private List<String> fromListText(String property) {
		List<String> result = new ArrayList<String>();
		if (property.length()>0) { //an empty string as assumed to be an empty list, rather than a list with 1 empty string in it!
			StringReader reader = new StringReader(property);
			CSVParser csvReader = new CSVParser(reader);
			try {
				for (String v : csvReader.getLine()) {
					result.add(v);
				}
			} catch (IOException e) {
				logger.error("Exception occurred parsing CSV properties:"+property,e);
			}
		}
		return result;
	}

	/**
	 * Set a value that is known to be a list. The value can be retrieved using this{@link #getPropertyStringList(String)}
	 * <br>
	 * Within the file, the value is stored as a single Comma Separated Value
	 */
	public void setPropertyStringList(String key, List<String> value) {
		setProperty(key, toListText(value));
	}

	private String toListText(List<String> values) {
		StringWriter writer = new StringWriter();
		CSVPrinter csvWriter = new CSVPrinter(writer);
		csvWriter.println(values.toArray(new String[]{}));
		return writer.getBuffer().toString().trim();
	}

}